1. Field of the Invention
The present invention relates to a method for analyzing a substance that has been developed over a membrane in a solid phase by using a laser desorption ionization mass spectrometric method and a sample plate used in such a method, in various fields such as clinical, diagnostic, biochemical and molecular biological fields.
2. Description of the Background Art
In order to analyze a mass of molecules to be measured, a laser desorption ionization mass spectrometric method has been used in which a laser beam is applied to a sample placed on a sample plate attached to a mass spectrometer so that the sample is ionized and analyzed (see JP-A No. 10-40858). Upon placing the sample on the sample plate so as to be analyzed, there are two methods, that is, one method in which a matrix is used and the other method in which a matrix is not used.
A method in which the method using a matrix is combined with a time-of-flight mass spectrometer is referred to as MALDI-TOF (matrix-assisted laser desorption ionization time-of-flight) mass spectrometric method.
The MALDI-TOF mass spectrometric method is a technique capable of analyzing molecules ranging from a low molecular weight to a high molecular weight, quickly with high sensitivity. In particular, this method exerts superior capabilities in analyzing biological samples such as proteins, peptides and nucleic acid molecules.
In the case where a measuring sample is given as a mixture, with respect to the sample, normally, molecules to be measured are selected in a separated state through gel electrophoresis, and after being extracted from the gel through various reactions, the sample is placed on a metal sample plate together with a matrix solution.
Here, with respect to the measuring sample, a mass spectrometric method has been proposed in which after biomolecules have been separated through electrophoresis or the like, these are transferred onto a membrane in a solid phase, and the solid-phase sample is subjected to various reactions on the membrane by utilizing a trace-amount application technique using a piezoelectric element, and the resulting reaction products are utilized to carry out mass analysis (see International Publication No. WO98/47006).
In order to achieve a system in which the sample, separated through gel electrophoresis, is transferred onto a membrane, subjected to a reaction by applying trace amounts of various reagents thereto, and introduced into a mass spectrometer, complex operations are required in respective steps or transit states between the steps. In other words, the respective operations are independent individually, and no systematic compatibility is prepared for these operations. For this reason, the membrane bearing the solid-phase sample is removed from the transferring device, and shifted to a stage for trace-amount application processes, and then fixed onto a sample plate for mass spectrometry; therefore, the supporting members for the membrane need to be changed in the respective stages.
The above explanation has exemplified a case in which the sample for use in MALDI-TOF measurements is prepared. However, the same problem arises also in the case where the sample is prepared without using a matrix.